The invention relates to an apparatus for cheking the presence of liquid at a predetermined level in a container, particularly in the crank case of an internal combustion engine.
Fluid level indicators are known, in which is disposed at the end of a pipe dipping into the liquid a valve, in which a valve body, for example a ball, is pressed against a valve seat by the rising liquid under the effect of a reduced pressure produced by a suction pump, whereby a reduced pressure, which serves for the indication of fluid level, arises in the suction duct of the pump. The valve in that case is so dimensioned, that the valve body is not pressed against the valve seat by the generated reduced pressure, when no liquid is present in the region of the suction opening at the end of the suction duct. The disadvantage of such arrangements consists therein, that the valve is constantly disposed in the liquid, so that the danger exists particularly when oil containers shall be monitored, that the valve becomes polluted by such oil in the course of time and no longer functions unobjectionably, particularly when the valve is of small dimension, such as is unavoidable when the valve is used for monitoring of the oil level in the crank case of an internal combustion engine and the valve is to be introduceable through the bore of the usual oil dip stick.
Not to bring the valve seat constantly into connection with the liquid and thus to reduce the danger of pollution and incrustation, it is known to construct the valve body not as a ball, but as a relatively long rod, which at its upper end is appropriately constructed for the co-operation with the valve seating. In the region of the valve body constructed as rod and of the valve seating, it is however necessary to construct the suction duct to be stiff to prevent a bonding of the suction duct and to ensure an unobjectionable displacement of the valve body in the suction duct. It is hereby however not always possible to introduce this apparatus through the bore of the usual oil dip stick in internal combustion engines, particularly when the guidance for the oil dip stick is constructed to arcuate. Beyond that, this construction affords no absolute security agaisnt a pollution of the valve seat and thus a faulty performance of the valve, even though the valve does not constantly dip into the liquid, yet liquid gets to the valve seat and the suction duct connected thereto during the checking process. Always according to the viscosity of the liquid, this will after completion of the checking process escape more slowly or more quickly from the valve, it not being avoidable here, that remnants remain, which lead to troubles in the course of time.